There has conventionally existed a video display device that has a display device in which a switching operation on a switch can manually switch between vertical display and horizontal display, and a video separation unit such as a parallax barrier or lenticular lens disposed on the front surface of the display device, wherein the display device combines left-eye image data and right-eye image data corresponding to the video separation unit into a single piece of parallax image data. There is also a video display device in which the position of the display screen in relation to the video display device is detected, to switch between vertical display and horizontal display of the video separation unit and the display device in accordance with the detected position (see, for example, Patent Literature 1).
FIG. 16 is a diagram showing the schematic configuration of the conventional video display device described in Patent Literature 1.
In FIG. 16, an observer observes a display device 201 through a video separation unit 202 located between the observer and the display device 201. In the display device 201, a reference pixel P(1, 1) is located at the upper left of the display device 201. A pixel row is configured by a plurality of subpixels arranged starting from the reference pixel P in an X-axis (+) direction, and a pixel column is configured by a plurality of subpixels arranged starting from the reference pixel P in a Y-axis (−) direction. The image data displayed in the display device 201 and the configuration of the parallax barrier of the video separation unit 202 are controlled using the information on the position of the display device 201 detected by a position sensor 203 of the video display device, so as to allow the observer to stereoscopically view the resultant video.
In addition, in the conventional video display device that has a display device for displaying a plurality of parallax images combined into one screen and a video separation unit fixed on the front surface of the display device, normal stereoscopic vision is possible only in the vertical or horizontal display state. On the other hand, there is a video display device capable of achieving stereoscopic vision in both the vertical and horizontal directions while having a fixed parallax barrier, by optimizing a barrier pattern of the parallax barrier and displaying a plurality of parallax images corresponding to the barrier pattern in a single screen, with the direction of the parallax images being oriented to the rotation angle of the display screen (see Patent Literature 2, for example).
FIGS. 17 and 18 are diagrams each showing the pixel arrangement of the conventional video display device described in Patent Literature 2.
FIG. 17 is a diagram showing a pixel arrangement pattern for four-viewpoints, in which the display device of the conventional video display device is in a first placement state. FIG. 18 is a diagram showing a pixel arrangement pattern for four-viewpoints, in which the display device of the conventional video display device is in a second placement state obtained by rotating the display device 90 degrees from the first placement state. An observer observes the video display device through an opening of the parallax barrier located on the front surface of the display device 201. Therefore, the arrangement pattern of subpixels in the display device 201 and the barrier pattern in the parallax barrier are optimized so that only a group of first-viewpoint pixels (B1, R1, G1) 211, for example, can be seen. Note that a group of pixels (R2, G2, B2) 212 corresponds to second-viewpoint pixels, a group of pixels (R3, G3, B3) 213 third-viewpoint pixels, and a group of pixels (R4, G4, B4) 214 fourth-viewpoint pixels.
Patent Literature 2, therefore, enables stereoscopic vision in both the vertical and horizontal display states in a single video display device.
For example, in the case where the video display device is placed on a desk with its display surface facing up, the conventional video display device, unfortunately, cannot determine the direction in which the observer observes the video display device, and therefore cannot always provide an ideal display condition to the observer.
Moreover, in a stationary-type video display device where the top and bottom of its display surface are not established, or in the case where observers are present at the top and bottom of the display surface, the conventional configuration need to create a composite parallax video based on a certain observer, as well as an inverted composite parallax video. In addition, there is not known a video display device that executes stereoscopic display in accordance with the positions of observers present at the top and bottom of the display surface, to allow the observers to stereoscopically view the images correctly and simultaneously.
Another problem with the conventional configuration is that, when an observer observes the video display device that is tilted, stereoscopic vision cannot be executed correctly because the conventional configuration only executes vertical display or horizontal display.